Interesting info about that Alaska Airlines flight. Yeah, luckily nobody was sitting next to that "door plug" when it blew out. But one might ask, why wasn't it an operational escape door? And the answer is, because the plane was certified for a lower number of passengers, it didn't need to be (perhaps as a cost saving measure). Even more interesting, there'd be no way for a passenger to know they were sitting next to such a "plug" from the inside. Only from the outside would the door outline apparently be visible, from the inside it reportedly just looked like any other portion of the interior fuselage with an ordinary window.
@lauren Apparently the escape door is required in the high density flights like RyanAir (a number of safety exits per number of passengers), and instead of making two versions of the plane, they "cheated." One plane design, just fill the hole in one version.
The version Alaskan had is the one that's harder to reconfigure: another version offered by Boeing that's easier to reconfigure is to leave most of the door hardware intact, but install a blank piece of wall inside instead of the interior of the door. (Source: YT video nw4eQGAmXQ0)
